Why do some attributes start with '@' while others done't?

[Dibyendu Majumdar via Digitalmars-d]

On Thursday, 21 January 2016 at 23:18:16 UTC, tsbockman wrote:
> A revision of D that wasn't constrained by backwards 
> compatibility would almost certainly either require all 
> attributes to be prefixed by @, or change the grammar such that 
> attribute names could be reused as identifier names without 
> introducing ambiguities.

It seems to me that '@' could be allowed as optional prefix to 
attributes that currently don't have it without breaking code - 
or am I being naïve?